Lecture IX —129— Structure 



they are large and spherical in Monodea (Cavers, 1903). They occur 

 in older prothalli of Ophioglossum (Bruchmann, 1904; Campbell, 

 1908) while in prothalli of Botrychium thin-walled vesicles are often 

 so abundant as to fill the cells with a botryose mass (Jeffrey, 1898). 

 Baas-Becking (1923) said of Botrychium: "The so-called vesicles 

 occur, thin-walled, apparently osmotic products, filling sometimes the 

 whole cell ; or two vesicles may occur in a cell." 



Arbuscles : — These are said to be even more constant than vesicles 

 but more delicate and difficult to observe. It was the privilege of 

 Gallaud (1905) to describe these organs which had escaped earlier 

 observers. He said that a branch of an intercellular hypha enters 

 the cell-wall and within the cell gives off 3-4 new branches and then 

 dichotomises until it forms what looks like a floccose mass. These 

 ramifications enter into the host's protoplasm. "A cause de leur forme 

 generale rappelant en petit celle d'un arbre tres chevelu j'appelerai 

 arbuscles ces formations singulieres tres importantes sur lesquelles 

 j'aurai a revenir plus longuement." An arbuscle terminates the ex- 

 tension of each hypha. Gallaud thought that arbuscles are absorbing 

 organs (organe absorbant ou sugoir). They are simple or composite 

 (arbuscles composes) when a complex of arbuscles, sporangioles and 

 hyphae. Vuillemin thought that arbuscles are less a characteristic 

 production of the endophyte and more a result of the reaction of the 

 host-cells to invasion by a foreign body. 



Digestion of arbuscles by the host results in formation of the 

 sporangioles of Janse, otherwise called "prosporidi" by Petri. Janse 

 said : "These sporangioles, as I call them, owe their embossed aspect 

 to the relief which the spherical bodies that are contained in the in- 

 terior cast under the extremely thin membrane, bodies which I desig- 

 nate by the name of 'spherules'. The spherules are filled with a 

 quantity of little 'granules'. In spite of the name of sporangioles which 

 I give to these organs, I am far from affirming that they have a part 

 in the propagation of the endophyte. It must be stated, however, that 

 they are found, with only two or three exceptions, among all the plants 

 which I have studied." Gallaud said that transformation of arbuscles 

 into sporangioles is almost always very rapid, and Janse noted in a 

 number of the plants he investigated that the sporangioles later freed 

 their content to form a gummy mass, or at maturity, they formed very 

 fine granules that diffused through the cell. And Endrigkeit (1937) 

 decided that intracellular arbuscles cannot be interpreted as assimila- 

 tory organs since they are digested as they are formed and show no 

 indication of hyphal development from their terminal branches, but 



